1. Field of the Invention
This invention relates to the field of engine starter gearing. More particularly, this invention relates to engine starter gearing of the non-indexing, positive shift dentil teeth type overrunning clutch starter gearing.
2. Description of the Prior Art
Clutches of the general type described herein above are well known in the art, but the art teaches that such drives require rather complicated mechanisms to separate the dentils of the overrunning clutch. An example of such drive is illustrated in U.S. Pat. No. 3,263,509, by Digby, assigned to the assignee hereof. Such starter gearing mechanisms as illustrated in the above noted letters patent renders these drives suitable only for large engine installations, primarily large volume displacement diesel engines. A similar type of overrunning clutch suitable for smaller engine installations, i.e., engine installations requiring less than 70 ft. lb. of steady state torque during cranking, is illustrated in U.S. Pat. No. 3,714,834 by Digby, also assigned to the assignee hereof. Initial development criteria of the smaller engine drive starters required the removing of the complicated dentil separation mechanism and reducing the drive in size in order to meet the objectives of suitability for smaller engine installations. However, such starter gearing suffered from a major defect, that is, the drive which was initially very reliable, eventually (within as little as one-fifth of its expected life) began to suffer an impositiveness in engagement with the engine to be started. Initial examination of such drives has shown that a tooth abutment between the pinion gear and the gear of the engine to be started prevented engagement of the drive and allowed sufficient axial movement of the shifting mechanism for the starter motor contacts to be closed, thereby causing the power shaft to rotate. Such action occurring without the interengagement of the pinion and the ring gear of the engine resulted in tooth milling, either of the ring gear or of the pinion gear, which thereafter required expensive and time consuming replacement. To solve this initial problem, it was believed that the use of a bearing sleeve underneath the pinion gear, as well as a thrust bearing interconnecting the pinion gear and starter gearing sleeve which couples the starter gearing to the rotary power shaft, would eliminate this problem. By providing an intermediate low friction member, or washer, between a high speed rotating pinion and a comparatively low speed rotating body (the bearing sleeve) the amount of rotary energy being transmitted from the pinion to the sleeve was minimized. However, the use of the bearing sleeve in conjunction with the thrust body restricted the use of a pinion gear to a size larger than the smallest sized pinion used on many of the small engine installations for this type of drive. Further, the interaction of the helical splines was such as to cause a severe axial load on the stop mounted to the power shaft, so as to result in some breakage of the shaft under these conditions. Also, the bearing sleeve had to be brazed to the body which is an expensive process and has caused problems, such as breaking loose from the body to which it is brazed.
U.S. Pat. No. 4,019,393 by Mortensen, also assigned to the assignee hereof, provided engine starter gearing with a dentil type overrunning clutch that assured high torque transmitting capabilities and was further provided with a third sleeve which permitted collapsing of the internal starter gear members to enable the rotary thrust loads to be absorbed by a resilient member internal of the starter gearing. By providing the internal members to cause the torsional shock to be absorbed by the resilient member, it was possible to eliminate the bearing sleeve and thereby allow starter gear usage in applications theretofore unable to be serviced. The third sleeve member utilized a straight spline to enable the rotary thrust energy to be transmitted to the resilient member thereby eliminating the need of a bearing member under the pinion gear. However, in practice, space requirements for such engine starter gearing usually require use of the embodiment of the invention of the aforesaid U.S. Pat. No. 4,019,393 that was illustrated in FIG. 2 thereof, an embodiment requiring the use of a complex and expensive one-piece load bearing housing member with a load bearing helical spline on the inside surface thereof.